1. Technical Field
The present invention relates to an actuator, an optical scanner, and an image formation apparatus.
2. Related Art
There is a known actuator using a structure including a torsional oscillator formed by processing a silicon substrate by using a MEMS (micro electro mechanical systems) technology (see JP-A-8-322227, for example). An actuator of this type is used as an optical scanner that scans an object with light in a printer, a display, and other apparatus.
For example, the actuator described in JP-A-8-322227 includes an inner movable plate having a flat-plate-like shape, a pair of second torsion bars that swingably support the inner movable plate, an outer movable plate having a frame-like shape, and first torsion bars that swingably support the outer movable plate. The thus configured actuator further includes a flat coil provided on each of the inner movable plate and the outer movable plate and permanent magnets disposed in fixed positions, and interaction between magnetic fields produced by the flat coils and the permanent magnets produces pivotal motion of the movable portions.
In the actuator described above, wiring lines from the flat coils are electrically connected to outer electrode terminals via the first torsion bars.
Further, the structure including the inner movable plate, the outer movable plate, the first torsion bars, and the second torsion bars is formed by etching a silicon substrate.
As described above, the fact that the wiring lines from the flat coils provided on the movable plates are electrically connected to the outer electrode terminals via the first torsion bars causes the distance between the flat coils and the permanent magnets disposed in fixed positions to be undesirably long.